A single-line diagram of a four-bus system is shown in Figure. Equipment ratings and per- unit reactances are given as f

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A Single Line Diagram Of A Four Bus System Is Shown In Figure Equipment Ratings And Per Unit Reactances Are Given As F 1 (67.52 KiB) Viewed 28 times

A single-line diagram of a four-bus system is shown in Figure. Equipment ratings and per- unit reactances are given as follows. Machines 1 and 2: 100 MVA Transformers T₁ and T2: 20 kV X₁ X₂ = 0.2 Xo = 0.04 X₁ = 0.05 100 MVA > On a base of 100 MVA and 345 kV in the zone of the transmission line, the series reactances of the transmission line are X₁ = X₂ = 0.15 and Xo = 0.5 per unit. The sequence impedance networks for the system are given below. a) Assume the system to be operating at nominal system voltage without prefault currents when a bolted line-to-line fault occurs at bus 3. Compute the fault currents of the three phases, the phase voltages at the faulted bus, and the phase voltages at the bus 4. b) Now, assume the system to be operating at nominal system voltage without prefault currents, when a bolted double line-to-ground fault occurs at bus 4. Compute the fault current of the three phases and the phase voltages at the faulted bus. 1 T₁ 2 Machine 1 Fry 101 20A/345YkV X₁ X₂ = Xo = 0.08 Δ' T₂ 4 HO YA Machine 2 yoong